Evening Star Newspaper, March 29, 1931, Page 83

THE SUNDAY STAR, WASHINGTON, D. C, MARCH 29, 1931. FOR OCEAN SHIPS New Marvel Produced by Science for Navi- gation Makes It Possible for Vessel to Find Correct Location and Proceed Safely on Desired Course, Despite Storm-Swept Sea and Sky. BY HARRY GOLDBERG. T was noon by the clocks. The sun rode at its highest in the heavens, but it was nowhere to be secen. Dark clouds shut out every ray from this blazing ball of light. The sea was as somber as the sky, while a great ocean liner, bound for New York, wes nosing its way somewhere in the vast Atlantic. Just as seamen have done every day for some 500 years, the officers stood waiting on the bridge with their sextants ready to “shoot” the solar disc and so locate the position of the liner. With the sun beaming down they could measure where they were and the ship could be pointed accurately on her course. But high above lay ® heavy haze of cloud and fog. Compass errors and currents shift even the mightiest vessels from their way upon these watery tracks and the noontime check is im- portant to head the ship precisely toward its port of destination. If this fog curtain hung stubbornly between the ship and the sun the skipper would have no recourse but to make the best guess he could and, using a series of calcu- lations, locate hims-lf by dead reckoning. So Columbus and John Cabot, Hendrik Hud- son and Magellan, with less charts and lesser mathematics, had also fumbled and figured when nature was hostile and chose to keep the sun out of sight. But a breezz blew, the clouds parted and the sun beat through. The four men, sighting their sextants, “shot” the position of the sun and each man reported his findings of the latitude. The two extremes were found to be one and a half minutes apart. In this latitude a minute of distance on the map is a mile. The four readings were averagod and the mean was taken as the true position of the liner, A TRUNK stood on the bridge. An upright rod rose from it holding a metal drum, Beneath the drum hung a sextant, and as the elouds closed in again and the sun once more disappeared behind the blackness, Paul Hum- phrey Macneil, the inventer, stepped up to the spparatus. He turned a few screws and dials and a needle swung boclia.nd forth until finally it reached the maximum on a graduated scale. He turned it over to Capt. S. G. 8. McNeil of the ship for reading. The captain of the ship and the inventor have names of the same pro- nunciation, but spelled differently. The skipper gazed at the scale in astonish- ment. “Why,” he exclaimed, “it is within one minute of the correct latitude.” “How do we know what is correct?” asked Staff Ca2pt. F. W. Robinson, who was also on the bridge. “Our sextant observations vary a8 much as one minute and a half, while this instrument is only one minute away from the average reading of our four.” With the sun completely obscured, a sextant reading locating the position of a ship by the position of the sun had been taken for the first time in the long history of navigation. “I really believe,” said Mr. Macneil, “that the all-weather sextant was more accurate than the observations taken by the four officers with their hand instruments. Their reading was subject to human error, while mine was taken by a mechanically and scientifically accurate instrument.” Mr. Macneil’'s combination of wires and lights, glass, metal and gelatin is the first real advance in this phase of the art of navigation since mariners began to use a simple cross bar, steadied by hand, to take observations of the sun and translate them with nautical tables into the latitude of that spot on the sea. The cross bar developed into the astrolabe and then into the sextant, which was used by Thomas Godfrey of Philadelphia in 1730. Tycho Brahe, the astronomer; Isaac Newton, one of the mental giants of all time, and other brilliant men played with the idea, but nothing but re- finements were developed in the instrument until the present knowledge of light and elec- tricity made the all-weather sextant possible. “It is really a wonderful invention,” said Capt. McNeil, describing his epoch-making test of the scientific eye which penetrated the fog. “When it is perfected it will revolutionize navi- gation. I can only say that I was amazed at the results. “When I made the tests the sun was ob- scured by heavy, black, low-hanging clouds, and if Mr. Macneil's invention could plerce them as it did and record the true altitude of the sun as it did, then I am confident that it could penetrate the densest fog at sea. “It is easy to foresee what this means to world transportation, both on the sea and in the air, should such a sextant come into general use. It means there no longer will be a neces- sity for dead.reckoning. It means that a ship may proceed true upon her course in all weather and it means that the usual delays oc- casioned by fog will be minimized, thus effect- ing a great saving in time and money.” Tms revolutionary sextant has been eight years in the making. It has a reflesting disc which works in conjunction with a series of crystals and which will pick up nothing but infra-red rays of a certain length. The reflec- the dark heavens and strikes the reflector. The t of strongest light gives a direct focus on the inventor was working on his idea discouraged by many famous physicists, said he could not find the sun through fog way he was planning. one man in the world gave me hope,” . Macneil, “and that was Dr. Moll of University of Utrecht, Holland. Others had worked on the use of the infra-red rays of the sun, but they limited themselves to shorter rays in that band. They found that the moisture in the atmosphere during fog completely absorbed all the rays of the sun and therefore no appa- ratus looking for infra-red or any other kind of familiar ray could find the sun’'s position.” In &sm course of his experiments Mr. Macneil found that there was a reradiation of rays through the clouds and that these were infra- red rays, about which little was known and which were many times longer than those usu- ally studied. “If you touch a match to a metal plate it will heat up,” he said, “but if you measure the heat emitted on the other side of the plate you are Here is the Macneil all-weather sextant, whick was tested successfilly on @ recent ocean voyage. not measuring the heat of the match but thg reradiation of the heat from the metal.” g These reradiated rays are the ones which hig device uses and the all-weather sextant ig founded upon the principle of using the rays on the visible side of the cloud or fog to focus on the sun. It is in two parts, one the actual sex- tant and the other an amplifier. The sextant portion is similar in appearance to the ordinary sextant, but it operates in an entirely different manner, Before the special reflector concentrates the invisible infra-red rays and focuses them on the detector, gelatin screens intercept the light and filter out all the rays except those of the longer infra-red radiations. Flexible wires carry the infinitesimal current which has been generated from the sensitive detector to a special amplifier and the ampli- fied current is then carried back by another wire to an indicating scale on the sextant. The detector is so delicate that it will pick up one microvolt—a millionth of a volt—and the amplifier so powerful that it will amplify 250,000 times. Thus far Mr. Macneil has noé found it necessary to use the full range of the amplifier. In the low visibility of ordinary bad weather during the tests it was only necessary to step up the detected current about 2500 times. According to the inventor, the amplifier will not be affected by the movement of the ship. In order to study the effect of vibration upon it he has taken the instrument up in an airplane and operated it efficlently without disturbance of its accuracy. WHAT makes possible the success of the all- weather sextant is the fact that the longer infra-red rays are reradiated in a direct line from the short waves on the other side of the clouds. Therefore, when the indicator shows that the reflector has been focused om the maximum point of infra-red rays, it gives scientific evidence that the sextant is focused directly upon the sun. The sextant is used in the same way that navigators have been using such an instrumen§ since the primitive cross bar came irnto use some time in the fifteenth century, except the instead of viewing an image of the sun, th® navigator views the indicating meter which electrically records the fact that the instrumens is in focus. To insure precision of the focus on the re= flector, the rays are required to pass throughy & diaphragm having an aperture of about ong millimeter, which is about the diameter of the sun as it would be if it shone down unobscured upon the reflector at that distance. The in- strument is accurate to about 20 minutes of latitude, according to the inventor. Mr. Maeneil's first experiments, made at his home in Huntington, Long Island, were conduct- ed upon an instrument imbedded in a concrete base and so sensitive that it registered the heat of a man’s hand placed near it. His present device contains an element similar in principle to the thermo-couple used by astronomers te measure the heat of distant stars. With the new form of sextant, says the in- ventor, the navigator can get the true altitude of the sun at any time without difficulty as long as the sun is above the horizon. The instru- ment was made in its present form with the familiar sextant attached so as not to break too sharply with the practices of the past and the present, and not to stir up the prejudices of old sallors who have been using sextant readings for a lifetime. At the present ttme, addition of the reflector Coutinued on Bightsenth Page